Method and apparatus fof feeding and guiding logs to woodworking machines

ABSTRACT

Feeding and guiding logs wherein the log is moved longitudinally and engaged on its opposite sides for centering along the axis of the feed path. After centering, the top of the log is engaged and held down in centered position on the feed path. The log may be again centered and held down one or more times to insure proper positioning of the log. Prior to centering, the feed path is comprised of two longitudinally aligned conveyors which may be tilted toward each other, so that when the log is positioned on both of the conveyors, it will contact essentially only two points thereof enabling the log to rotate about is own axis in the event the weight of the log is unevenly distributed. In addition, a lifting and rotating device may be positioned between the conveyors to lift and rotate the log about its axis to insure the centering point of the log is properly positioned with respect to the path of conveyance.

United States Patent METHOD AND APPARATUS FOF FEEDING AND GUIDING LOGS TO WOODWORKING MACHINES 24 Claims, 6 Drawing Figs.

US. Cl 198/29,

143/49, 198/33 AC Int. Cl 865g 47/24 Field ofScarch 198/29, 33

R; 143/49, 55; l44/245.l, 253.3

[56] References Cited UNITED STATES PATENTS 2,821,220 [/1958 Nicholson 143/49 3,089,576 5/1963 Sauer et al. 198/29 Primary Examiner-Andres H. Nielsen Attorney-Beveridge & De Grandi ABSTRACT: Feeding and guiding logs wherein the log is moved longitudinally and engaged on its opposite sidesfor centering along the axis of the feed path. After centering. the top of the log is engaged and held down in centered position on the feed path. The log may be again centered and held down one or more times to insure proper positioning of the log. Prior to centering, the feed path is comprised of two longitudinally aligned conveyors which may be tilted toward each other, so that when the log is positioned on both of the conveyors, it will contact essentially only two points thereof enabling the log to rotate about is own axis in the event the weight of the log is unevenly distributed. in addition, a lifting and rotating device may be positioned between the conveyors to lift and rotate the log about its axis to insure the centering point of the log is properly positioned with respect to the path ofconveyance.

PATENTEUNEIYZBIHTI 3.621.972

SHEEIlUF3 I Inventor:

ALFRED REUTER PATENTEDNHV 23 an 3. e21 .972

sum 2 [IF 3 Inventor:

A LF RED vTE TL PAIENTEUuuv 23191:

SHEET 3 BF 3 Inventor: A LFRED QEUTEK W41)? {DO CXWQQ METHOD AND APPARATUS FOF FEEDING AND GUIDING LOGS TO WOODWORKING MACHINES SUMMARY OF THE INVENTION This invention relates to method and apparatus for feeding and guiding logs into woodworking machines, such as for example, frame saws, profile chipping machines. The present invention employs an essentially horizontal continuous conveying installation for transporting the log; such installation may be, for example, a chain bed, conveyor belt or roller bed.

Feed arrangements known in the prior art employ continuously revolving conveying chain arrangements, so-called chain beds, to feed the logs to a woodworking machine. These known installations have among other drawbacks the disadvantage of being unable to feed both raw logs as well as logs which have already been precut on two opposing sides, socalled cants.

It is an object of the present invention to overcome the aforementioned disadvantage through the provision of a novel method and apparatus for feeding both raw logs as well as cants.

It is a further object to provide such a feeding method and apparatus which will fed logs or cants aligned with the longitudinal axis of the conveyance path and with the logs lying in firm position on the conveying installation.

According to the invention, the above objects are achieved through at least two pairs of centering devices disposed on opposite sides of a horizontal conveyor which press the log into the middle of the conveyor, and through at least one holddown device which holds the log down on the conveyor. Through these devices controlled positioning of the log on the conveyor will be achieved, while the holddown device presses the log against the conveyor bed and thus makes possible its conveyance by the conveyor to the woodworking machine. With this arrangement it will not only be possible to feed untreated logs, but also cants.

In accordance with one embodiment of the invention, each pair of centering devices is coupled to each other so that their centering movement inwardly toward the conveyor will take place symmetrically relative to the longitudinal center of the conveyor path. As a result, effective alignment of the log in relation to the center of the conveyor path is assured even though the log may have a strongly eccentric position which results in an uneven distribution of force on the two centering devices of each pair. In addition, it is preferred that each pair of centering devices be operable through a common hydraulic or pneumatic cylinder. Thus, only a single cylinder is required for each pair of centering devices which allows a simple coupling of the two centering devices in each pair as described above.

According to a further aspect of the invention, a reversing system is provided which responds at the passage of a log by the last pair of centering devices to decrease or neutralize the power of the centering devices while increasing the effective power of the holddown device. In this manner, the log can be initially aligned with the center of the conveyor path under the effective power of the centering devices without impedance by a greater pressure force exerted on the log by the holddown device. When, however, the log passes the last pair of centering devices, the alignment process has been completed, and the reversing system allows the holddown device to exert suffb cient force to hold the log firmly on the conveyor during the last phase of the feeding to the processing machine. At the same time, the reversing device causes withdrawal of the centering devices so that jamming of the log will be prevented.

The aforementioned system can be effectively achieved by operating the devices by hydraulic cylinders which are alternatively supplied with work fluid from highand low-pressure fluid sources. Thus, when a log is passing through the centering devices, the associated hydraulic cylinders are connected with the high-pressure fluid source while the holddown device is connected with the low-pressure fluid source. After the log passes the last pair of centering devices, their associated LII hydraulic cylinders will be connected with the low-pressure source while the holddown device will be connected to the high-pressure source. The reversing system can be carried out by a hydraulic reversing valve which will function to alternatively connect the centering devices and holddown devices with the highand low-pressure sources. In this manner, the desired reversal of the power effect between the centering devices and the holddown devices can be achieved effectively and very rapidly. Whenever the two required pressures are always available as operating pressures of two separate pressure supply sources, the reversal of power for driving the centering and holddown devices can be achieved in a rapid and simple manner through a hydraulic reversing valve.

It is preferred that the centering and/or holddown devices be pivotable about an axis running transverse to the conveying direction. This makes possible good guidance of these devices while providing good adaptability to the differing dimensions and positions of the log. The centering and holddown devices may each have movable chains, rollers or conveyor belts rolling off along the log during the conveying movement. In this manner, resistance to movement of the log will be lowered. The chains, rollers or conveyor belts incorporating the devices may be driven synchronously with the conveyor in order to aid feeding of the log by the conveyor and thereby to relieve the drive mechanism of the conveyor.

The centering devices and/or the holddown devices may alternatively comprises swinging flaps pivotally mounted at an angle to the longitudinal direction of the log and conveyor path. These flaps may have a simple structure and also adapt themselves easily to differing dimensions and positions of the logs.

For practical purposes, the last pair of centering devices reached by the logs operates the reversing valve as soon as the beginning of the log upon its passage swings the two centering devices apart. Through this arrangement, the reversal will take place precisely at the point in time when the centering device reached last will have aligned the beginning of the log.

According to a still further advantageous feature of the present invention, the chain bed of the conveyor is provided with teeth to grasp the log, which, however, for practical purposes, are at the most so large that a slipping of the teeth along the log takes place before a permissible chain force will be surpassed. The teeth guarantee the log being carried along by the chains, but at the same time they make possible a slipping of the chains whenever the force occuring along the teeth surpasses a permissible value.

In accordance with a further aspect of the invention, the beginning of the conveying installation is formed by two conveyors each arranged in a separate frame which is pivoted about a horizontal axis running transversely to the conveying direction. Each conveyor may be pivoted to an inclined position in relation to one another before the log is conveyed to the centering devices. This facilitates turning of the log about its longitudinal axis by a lifting and rotary device positioned between the two conveyors. This enables the heaviest point on the log to be positioned downwards so that the log will firmly rest on the conveyor bed. The log lifting and rotating device may be provided by two rollers with a revolving axis running essentially in the conveying direction, one of which rollers at least can be driven. But instead of that or besides that, it may also have a band or a chain running transversely to the conveying direction with the help of which the log can be turned. The rollers are positioned below the conveyor path between the two conveyors to contact the log.

Further objects and advantages of the invention will be apparent from the attached drawings as well as from the following description.

DESCRIPTION OF DRAWINGS FIG. 1 is a side elevational view of apparatus embodying the invention;

FIG. 2 is a plan view of the apparatus of FIG. I;

FIG. 3 is a schematic side view of centering and holddown devices and associated hydraulic system incorporated in the apparatus;

FIG. 4 is a plan view of the devices shown in FIG. 3;

FIG. '5 is a schematic side view-of two conveyors at the inlet section of the apparatus with the conveyors shown in inclined positions; and

FIG. 6 is a view similar to FIG. 5, but with the conveyors in horizontal position.

DETAILED DESCRIPTION In FIG. 1, a profile chipping machine 1 has been shown as an example of a woodworking machine to which logs may be fed in accordance with the present invention. The conveying installation for feeding the logs or cants consists of three chain beds 2, 3 and 4 arranged one behind the other, each of which is formed by several conveying chains revolving endlessly and arranged one beside the other. The first bed of chains 2 is mounted swivelably with its frame 5 around the axis 6. A pivot drive, for example a hydraulic cylinder 7, produces the pivoting of the frame 5. The second chain bed 3 is mounted swivelably with its frame 11 by means of axis 12. The swivel cylinder 13 brings about the swiveling movement.

Between the chain beds 2 and 3, there is a log lifting and turning device 17 in which two drivable rollers 18 and 19 are mounted with a rotational axis running the longitudinal direction of the conveying installation. The upper part of the rotating arrangement 17, bearing the rollers 18 and 19, can be lifted by means of a suitable hydraulic device (not shown).

Immediately in front of the woodworking machine 1, there is the third chain bed 4, over which a frame structure 20 is erected. Holddown devices 21 and 22 are disposed on frame structure 20. Laterally beside the chain bed are centering devices 23, 24 and 25, 26 arranged in pairs.

l-lolddown devices 21, 22 (FIG. 3) have conveying chains 31 and 32 which are driven by one common driving engine 33 (FIG. 1). Holddown devices 21 and 22 are each mounted swivelably with one around an axis 37 or 34 in the frame structure 20. Hydraulic cylinders 35 or 36, likewise arranged in frame structure 20, will swing the holddown devices 21 and 22 around axes 37 and 34.

The other pair of centering devices 23 and 24 have conveying chains 41 and 42, which can be swung around axes 43 and 44 and which are driven by operating engines 45 and 46. Both centering devices 23 and 24 are connected via toggle levers 48 and 49 with a common hydraulic cylinder 47 for the purpose of carrying out the swinging movement. The second pair of centering devices are formed by flaps and 26, which can pivot around axes 52 and 53. The pivoting movement is brought about via levers 55 and 56 by means of a common hydraulic cylinder 54.

The hydraulic installations for swinging holddown devices and centering devices consists essentially of a high-pressure pump 60 with a high-pressure-adjusting valve 61 and a lowpressure pump 62 with a low-pressure-adjusting valve 63. Both hydraulic parts of the installation are connected with hydraulic cylinders 35, 36 or 47, 54 via a reversing valve 64. A thermal switch 65 arranged on centering units 25 and 26 can be switched through the swinging movement of the centering devices to operate reversing valve 64.

The arrangement according to the invention operates as follows. Initially, the log reaches the driven chain beds 2 and 3 (FIG. 5) inclined in relation to one another and in doing so it revolves into such a position that its center of gravity reaches the deepest point in relation to. the two points of support. Through lifting the revolving device 17 with the rollers 18 and 19, the operator can support the turning process and impart to the log the position which will be most favorable for further treatment, that is to. say that position in which the log will rest as completely as possible on the conveyors.

If instead of an untreated or raw log, a cant which has already been worked on two opposite sides, is to be fed (FIG.

6), then. chain beds 2 and 3 are set horizontally, since now a turningof the workpieceis not necessary; the turning device 17 will remain out of operation.

When the log or cant reaches chain bed 4 which has been equipped withfine teeth, the log or cant moves toward woodworking machine 1 and first of all makes contact with centering chains 4! and 42 of the first centering device arranged laterally andrdriven synchronously with the chain bed. The chains will seize the log or the cant and will prevent the log from turning around its own axis. As a result, the log will be prevented from changing again its favorable turning the position reached previously. The centering chains 41 open symmetrically because they are positively connected with one another via hydraulic cylinder 47. At the same time the hydraulic cylinder 47 is connected with hydraulic high-pressure installation; the two chains 41 and 42 are swung apart counter to the effect of the pressure agent being under high pressure. Since the chains can move only symmetrically in relation and toward the middle of the chain bed 4, the centering chains 41 and 42 align the log or the cant centrally relative to the axis of the conveyor bed.

The log or cant then moves below the holddown device 21 likewise driven synchronously with chain bed 4. This is accomplished without any particularly large expenditure of power since the hydraulic cylinder 35 of the holddown device 21 is connected this time with the low-pressure supply installation. Next the log or cant strikes against flaps 25 and 26 which form the second pair of centering devices. The common hydraulic cylinder 54 of the two flaps 25 and 26, which can only be swung symmetrically toward the middle of chain bed 4, is likewise connected with the hydraulic high-pressure supply installation; flaps 25 and 26 upon entrance of the log exert a great force on the log as a result of which a central alignment of the log on the conveyor bed is achieved.

In the case of opening centering flaps 2'5 and 26, the terminal switch 65 is operated, which reverses hydraulic control switch 64 and thus reverses the pressure conditions between the lateral centering units 23, 24, 25, 26 and the holddown device 21. That is to say, the high oil pressure which compressed the lateral centering arrangements strongly and which centered the log or cant thus in transverse direction on chain bed 4, is conducted to hydraulic cylindrical 35 of the holddown device 21. AT the same time the hitherto low oil pressure is switched from the holddown arrangement 21 to the lateral centering devices 23, 24, 25, 26.

After reversal of the pressure conditions upon swinging flaps 25 and 26 apart, the aligned position of the log or of the cant will be maintained because holddown device 21 presses the log onto chain bed 4 equipped with fine teeth, whereby these teeth dig into the wood. A further change in position perhaps through the relatively weak forces of the lateral centering arrangements or through forces which are exerted by the woodworking machine 1 on the wood, is no longer possible from this time on.

In its further transportation the log will arrive below a second holddown device 22 which is constructed in the same way as holddown device 21, and whose hydraulic cylinder 36 is switched in the same manner as hydraulic cylinder 35 of the first holddown device 21. That is to say, hydraulic cylinder 36 is likewise connected to the high-pressure supply. In this aligned position the log or cant will reach the woodworking machine.

After the log or cant has passed through flaps 25 and 26, the latter. will close again and thermal switch 65 will again move reversing valve 64 into its starting position.

Depending on the length of the log, it may be advantageous to provide more than two centering devices or more holddown devices so that the centering of the log takes place across a longer path of movement.

In the case of the embodiment shown by way of example, the drive of chains 31 and 32, holddown devices 21 and 22, as well as chains 41 and 42 ofgentering devices 23 and 24, takes place synchronously with movement of chain bed 4, so that a drive. It is also possible to slip between the chains and the log will be avoided as much as possible. instead of the chains, conveyor belts or rollers may also be employed. It is also possible to do away with the drive of the chains, belts or rollers and to let them roll freely without make all of themes chains, rather than flaps.

lclaim:

1. Apparatus for feeding logs comprising in combination, conveyor means for moving logs along a generally horizontal path, centering means movable transversely of the conveyor means for moving a log towards alignment with the longitudinal axis of said path, and holddown means separate from said centering means acting from above said path for urging the log downwardly on said path.

2. Apparatus defined in claim I wherein said centering means includes a pair of centering devices positioned on opposite sides of said path to be movable towards and away from said path generally in horizontal planes.

3. Apparatus defined in claim 2 wherein said centering devices are pivotally mounted to swing towards and away from said path.

4. Apparatus defined in claim 3 further including drive and control means for moving said centering devices in unison and such that the centering devices are always symmetrically disposed on opposite sides of the axis of said path throughout their travel.

5. Apparatus defined in claim 4 wherein said drive and control means includes coupling means coupling said centering devices together and a hydraulic fluid motor for operating both centering devices through said coupling means.

6. Apparatus defined in claim 1 wherein said holddown means is located down path of said centering means.

7. Apparatus defined in claim 6 further including drive and control means for releasing the driving force on said centering devices and for increasing thedriving force on said holddown means after the log has been centered by said centering means.

8. Apparatus defined in claim 7 wherein said drive and control means includes a first fluid motor operatively connected to said centering means to drive the same, a second fluid motor operatively connected to said holddown means to drive the same, a source of high-pressure motivefluid, a source of low-pressure motive fluid, and reversing valve means for alternately connecting said sources of 'motive fluid with said first and second fluid motors;

9. Apparatus defined in claim 1 further including at least two of said centering means and two of said holddown means, said centering means being spaced along said path with one holddown means being located between said centering means and with the other holddown means being located down path of the last centering means.

10. Apparatus defined in claim 2 wherein said centering means includes a flap member which engages the log.

11. Apparatus defined in claim 1 wherein said holddown means includes a member pivoted at one end for swinging movement in a vertical plane parallel to said path and being free at the other end for engaging a log.

12. Apparatus defined in claim 1 wherein said conveyor means includes endless chains defining said path and for moving the logs along said path, said chains having teeth for engaging the log, said teeth being dimensioned so as to slide relative to the log when excessive driving forces are imparted to said chains.

13. Apparatus for feeding logs comprising in combination, conveyor means for moving logs along a generally horizontal path, centering means acting transversely of the conveyor means for moving a log towards alignment with the longitudinal axis of said path, holddown means acting from above said path for urging the logs downwardly on said path, and

means at an inlet section of said conveyor means for rotating the log about its longitudinal axis.

14. Apparatus defined in claim 13 wherein said last-recited means includes two rollers mounted for rotation about an axis generally parallel to said path and means for raising and lowering said rollers into and out of engagement with the underside of a log.

15. Apparatus for feeding logs comprising in combination, conveyor means for moving logs along a generally horizontal path, centering means acting transversely of the conveyor means for moving a log towards alignment with the longitudinal axis of said path, and holddown means acting from above said path for urging the log downwardly on said path, said conveyor means including frame mounted for pivotal movement about an axis transverse to said path intermediate the ends of the conveyor for changing the inclination of the conveyor path, and wherein there is further included a second conveyor means situated before said first conveyor means and in generally longitudinal alignment with said first conveyor means, said second conveyor means being situated adjacent the inlet end of said first conveyor means, said second conveyor means including a frame mounted for pivotal movement between its ends about an axis transverse to said pivotal path of conveyance for changing the inclination of its path whereby the paths of said first and second conveyor means may be inclined downwardly towards each other such that a log will contact said conveyor means only at essentially two points thereby permitting the log to rotate under its own weight about its longitudinal axis.

16. Apparatus defined in claim 15 further including logrotating means situated between said first and second conveyor means for positively engaging and rotating the log about its longitudinal axis. I

17. Apparatus defined in claim 16 further including means for raising and lowering said log-rotating means into and out of engagement with a log.

18. Apparatus defined in claim 17 wherein said log-rotating means includes a pair of rollers mounted for rotation about axes parallel to the path of conveyance.

19. A method of feeding logs comprising the steps of feeding a log horizontally generally along a conveyor path, moving members transversely of said path into engagement with opposite sides of said log to center the same on the longitudinal axis of said path, and holding the log down on said path after it is centered.

20. The method defined in claim 19 further including the step of decreasing the engagement of said members on said log while increasing the holddown engagement on the log after the log is centered.

21. The method defined in claim 19 further including the steps of again centering the log on the longitudinal axis of the path after it is held down and again holding the log down after it is centered the second time.

22. A method of feeding logs comprising the steps of feeding a log horizontally generally along a conveyor path, engaging opposite sides of said log to center the same on the longitudinal axis of said path, holding the log down on said path after it is centered, and rotating the log about its axis to properly position the center of gravity of the log towards the path prior to centering the log on the path.

23. The method defined in claim 22 wherein the log is rotated by placement on two conveyors inclined downwardly towards each other such that the log contacts the conveyors at two points respectively which permits the log to rotate under its own weight about its longitudinal axis.

24. Apparatus for feeding logs comprising in combination, conveyor means for moving logs along a generally horizontal path, centering means acting transversely of the conveyor means for moving a log towards alignment with the longitudinal axis of said path, and holddown means acting from above-said path for urging the logs downwardly on said path, said centering means including a pair of centering devices positioned on opposite sides of said path to be movable towards and away from said path generally in horizontal planes, said centering devices each including an endless movable member which engages the log. 

1. Apparatus for feeding logs comprising in combination, conveyer means for moving logs along a generally horizontal path, centering means movable transversely of the conveyer means for moving a log towards alignment with the longitudinal axis of said path, and holddown means separate from said centering means acting from above said path for urging the log downwardly on said path.
 2. Apparatus defined in claim 1 wherein said centering means includes a pair of centering devices positioned on opposite sides of said path to be movable towards and away from said path generally in horizontal planes.
 3. Apparatus defined in claim 2 wherein said centering devices are pivotally mounted to swing towards and away from said path.
 4. Apparatus defined in claim 3 further including drive and control means for moving said centering devices in unison and such that the centering devices are always symmetrically disposed on opposite sides of the axis of said path throughout their travel.
 5. Apparatus defined in claim 4 wherein said drive and control means includes coupling means coupling said centering devices together and a hydraulic fluid motor for operating both centering devices through said coupling means.
 6. Apparatus defined in claim 1 wherein said holddown means is located down path of said centering means.
 7. Apparatus defined in claim 6 further including drive and control means for releasing the driving force on said centering devices and for increasIng the driving force on said holddown means after the log has been centered by said centering means.
 8. Apparatus defined in claim 7 wherein said drive and control means includes a first fluid motor operatively connected to said centering means to drive the same, a second fluid motor operatively connected to said holddown means to drive the same, a source of high-pressure moTive fluid, a source of low-pressure motive fluid, and reversing valve means for alternately connecting said sources of motive fluid with said first and second fluid motors.
 9. Apparatus defined in claim 1 further including at least two of said centering means and two of said holddown means, said centering means being spaced along said path with one holddown means being located between said centering means and with the other holddown means being located down path of the last centering means.
 10. Apparatus defined in claim 2 wherein said centering means includes a flap member which engages the log.
 11. Apparatus defined in claim 1 wherein said holddown means includes a member pivoted at one end for swinging movement in a vertical plane parallel to said path and being free at the other end for engaging a log.
 12. Apparatus defined in claim 1 wherein said conveyer means includes endless chains defining said path and for moving the logs along said path, said chains having teeth for engaging the log, said teeth being dimensioned so as to slide relative to the log when excessive driving forces are imparted to said chains.
 13. Apparatus for feeding logs comprising in combination, conveyer means for moving logs along a generally horizontal path, centering means acting transversely of the conveyer means for moving a log towards alignment with the longitudinal axis of said path, holddown means acting from above said path for urging the logs downwardly on said path, and means at an inlet section of said conveyer means for rotating the log about its longitudinal axis.
 14. Apparatus defined in claim 13 wherein said last-recited means includes two rollers mounted for rotation about an axis generally parallel to said path and means for raising and lowering said rollers into and out of engagement with the underside of a log.
 15. Apparatus for feeding logs comprising in combination, conveyer means for moving logs along a generally horizontal path, centering means acting transversely of the conveyer means for moving a log towards alignment with the longitudinal axis of said path, and holddown means acting from above said path for urging the log downwardly on said path, said conveyer means including frame mounted for pivotal movement about an axis transverse to said path intermediate the ends of the conveyer for changing the inclination of the conveyer path, and wherein there is further included a second conveyer means situated before said first conveyer means and in generally longitudinal alignment with said first conveyer means, said second conveyer means being situated adjacent the inlet end of said first conveyer means, said second conveyer means including a frame mounted for pivotal movement between its ends about an axis transverse to said pivotal path of conveyance for changing the inclination of its path whereby the paths of said first and second conveyer means may be inclined downwardly towards each other such that a log will contact said conveyer means only at essentially two points thereby permitting the log to rotate under its own weight about its longitudinal axis.
 16. Apparatus defined in claim 15 further including log-rotating means situated between said first and second conveyer means for positively engaging and rotating the log about its longitudinal axis.
 17. Apparatus defined in claim 16 further including means for raising and lowering said log-rotating means into and out of engagement with a log.
 18. Apparatus defined in claim 17 wherein said log-rotating means includes a pair of rollers mounted for rotation about axes parallel to the path of conveyance.
 19. A method of feeding logs comprising the steps of feeding a log horizontally generally along a conveyer path, moving members transversely of said path into engagement with opposite sides of said log to center the same on the longitudinal axis of said path, and holding the log down on said path after it is centered.
 20. The method defined in claim 19 further including the step of decreaSing the engagement of said members on said log while increasing the holddown engagement on the log after the log is centered.
 21. The method defined in claim 19 further including the steps of again centering the log on the longitudinal axis of the path after it is held down and again holding the log down after it is centered the second time.
 22. A method of feeding logs comprising the steps of feeding a log horizontally generally along a conveyer path, engaging opposite sides of said log to center the same on the longitudinal axis of said path, holding the log down on said path after it is centered, and rotating the log about its axis to properly position the center of gravity of the log towards the path prior to centering the log on the path.
 23. The method defined in claim 22 wherein the log is rotated by placement on two conveyers inclined downwardly towards each other such that the log contacts the conveyers at two points respectively which permits the log to rotate under its own weight about its longitudinal axis.
 24. Apparatus for feeding logs comprising in combination, conveyer means for moving logs along a generally horizontal path, centering means acting transversely of the conveyer means for moving a log towards alignment with the longitudinal axis of said path, and holddown means acting from above-said path for urging the logs downwardly on said path, said centering means including a pair of centering devices positioned on opposite sides of said path to be movable towards and away from said path generally in horizontal planes, said centering devices each including an endless movable member which engages the log. 